1. Field of the Invention
The present invention generally relates to a signal detector of an engine for a vehicle, and particularly relates to a signal detector which is suitable for the engine for a two-wheeled motor vehicle having a starter.
2. Description of the Related Art
In an engine for a two-wheeled motor vehicle, it is preferable to mount a one-way clutch for a starter mechanism on a crankshaft in order to reduce a mechanical loss of power for starting the engine. Therefore, the one-way clutch is generally mounted on an end of the crankshaft. In addition to the one-way clutch, a generator rotor, a pulser rotor for outputting pulse signals for ignition signals, and the like, a sprocket for cam drive, and so on, are mounted on ends of the crankshaft, separately.
As one example of a common arrangement, the sprocket for cam drive is mounted on one end of the crankshaft, and the generator is mounted on the other end of the crankshaft, where the one-way clutch for the starter mechanism is mounted in juxtaposition with the generator on the other end.
According to the arrangement in which the generator and the one-way clutch are mounted in juxtaposition with each other on the other end of the crankshaft longitudinally, however, the generator projects outwardly in the longitudinal direction, and therefore it is necessary to increase the width of the crankcase (namely, the length of the crankshaft). Particularly, if the two-wheeled motor vehicle is equipped with a plurality of cylinders (for example, four cylinders) in juxtaposition in the direction of the crankshaft, and if the generator projects outwardly in the longitudinal direction, it is not possible to take a large bank angle.
There has also been provided an engine, as shown in FIG. 10, in which the one-way clutch 102 for the starter mechanism 101 is mounted on an end of the crankshaft 105 opposite an end thereof on which the generator 103 is mounted in order to diminish the projection of the generator, as disclosed in Japanese Laid-Open Patent Publication No. 8-86223. That is, in the engine shown in FIG. 10, the sprocket 110 for cam drive, the pulser rotor 111 and the one-way clutch 102 for the starter mechanism 101 are all mounted on the same end of the crankshaft 105, and a rotor 103a of the generator 103 is mounted on the other end of the crankshaft 105. There is arranged a sensor (for example, pulser coil) 112 for signal detection radially outside the pulser rotor 111, and the sensor 112 is mounted on the starter cover 115.
Also in the arrangement in which the one-way clutch 102 is mounted on the one end of the crankshaft 105 opposite the other end thereof on which the generator 103 is mounted as shown in FIG. 10, however, the pulser rotor 111, the sprocket 110 for cam drive and the one-way clutch 102 are all mounted in juxtaposition on the same end of the crankshaft 105. Namely, with this arrangement, it is difficult to make the dimension of the crankcase 120 in the direction of the crankshaft 105 smaller.